Apparatus for manufacturing cement-asbestos board



April 11, 1950 w. BERNARD -Er AL APPARATUS FOR 4IIANUFAC'I'URING CEMENT-ASBESTOS BOARD Filed Oct, .21, 1947 2 Sheets-Sheet 1 A Trae/yer -AsEsTos BOARD i April n, 195o w. gERNARp :TAL Armuus son umumcmmc cmn'r Filed oet. 21, 1947 2 `Sheets-Shea?. 2

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mN. A m u n ilr ml m Hl om hasta. 11, leso in preparing cement-asbestos board for commer- UNITED s'rA'ras PATEN'IV ortica APPABATUSI'OB MANUFACTURING CEMENT-BESTOS BOARD WilllamBemard JephBernanLWestmlington, N. J., .I to American Asbestos Industries. lne., l ley Heights, N. J., a ecrporationci'New Jersey Application omb'zi, im, sorua No. 'man l 7 (Cl. 9243) 'I'his invention relates to an apparatus for manufacturing cement-asbestos board such as is used, for example, in the fabrication of cement asbestos shingles. The instant invention is an improvement over l the apparatus and process shown, described and claimed in our co-pending application for Cev ment asbestos board, Serial No. 674.303. filed F18. 5 is a sectional view through the molding June 6, 1946. vat, the same being taken substantially along the It is an object of the present invention to Dr0 10 line S-l of Fig. 2. vide an improved apparatus which, with the same Referring now in detail to the drawings, il number of molding vats and the vsame width of 'denotes a molding vat which contains a thin carrier band, can make cement-asbestos board cement-asbestos mixture I2 known in the trade considerably faster than the machine shown in as a slurry. This slurry is delivered at a uniour said co-pending application. le form regulatable rate to a storage tank S. From It is another object of our inventlonto provide the storage tank the slurry is delivered by a an apparatus of the character described vin which pump P to an inlet trough I4, extending along single and laminated layers of cementasbestos one end of the molding vat. The overilow from are so treated that within a minute after a layer the molding vat runs into a discharge trough it has been picked up from the molding vat it forms a0 which is connected by a conduit C'to the storage part of a laminated board dry enough to be hantank in a manner more fully described. If dedled, and which accomplish this desirable result sired, the slurry can be fed by gravity from without artificially drying' the board, as in an the storage tank to the molding vat and the over. oven, to strengthen the same before storage flow pumped back tqthe storage tank. thereof. 25 The vat contains an imperforate, cylindrical p It is a further object of the invention to-procollector roll IB which rotates in the direction vide an apparatus of the character described which avoid all necessity for using artificial heat view through the upper portion ofthe molding vat, the same being taken-substantially along the line 2-2 of F13. 1;

Fig. 3 is a fragmentary, partially broken awa! plan view of the molding vat; and

Fig. 4 is a side view of the molding vat; and

2t disposed perpendicularly to the longitudinal axis of an endless, pervious, fibrous carrier band 22 arranged to travel over the top of the vat il. Said band is guided in its movement across the vat by an idly turning entry guide roll 24 and a wherein an improved system is used to separate pair `oi' cooperating exit guide rolls 28 and 28. slabs from the continuous cement-asbestos layer hereinafter described in detail. These guide rolls on the carrier band. sa deilne a path of travel for the band above the Other objects of the invention will in part be level of the topl of the molding vat, startin,v from obvious and in part hereinafter be pointed out. a horizontal line slightly above the top of the dis- The invention accordingly consists `in the feacharge trough i6 and slowly uniformly rising to tures of construction, combinations of elements a slightly greater height over the inlet trough I4. and arrangement of parts which will be exemplieo The collector roll is so located with respect to fled in the apparatus hereinafter described and of which the scope of application will be indicated cial sale. 3l

It is an additional object of the invention to provide an apparatus of the character described therein that the upper portion of 'the roll is above in the appended claims. normal level of the slurry in the vat and, further# In the accompanying drawings, in which is more, is slightly higher than the top of the vat. ShOWn One 0f the Various DOSSible embodiments 46 'I'he two ends of the collector roll, as will be seen of our invention, v r from Fig. 2, are spaced inwardly from the side Fig. 1 is a longitudinal sectional view through walls of the vat, the reason for this being pointed the molding and laminating section of a cementout shortly hereinafter. Said 'collector roll is asbestos board plant constructed in accordance shorter than the width of the carrier band 22 with our present invention, the background 60 and is centrally located with respect thereto. structure being omitted for clarity; The upper portion of the collector roll is spaced Fig. la is a similar view through the calenderbeneath the undersurface of the carrier band. ing section of said plant; This spacing is quite small but. nevertheless.

, 2 I Fig. 2 is an enlarged vertical central sectional indicated by the arrow C with a horizontal shaft the top of the vat and to the heicht of the slurry 3 must be provided and, in a satisfactorily operating form of a machine embodying our invention,

' is about A of an inch.

to raise above the normal levelof the slurry in the vat a localized quantity of slurry in the form of a squat wide column terminating at the undersurface of the carrier band, this raising being performed in such fashion that the elevated column of slurry is forced against the undersurface of the band over a limited zone, hereinafter referred to as the pressure zone.

The upper portion of the collector roll operates in what, to all intents and purposes, is a .shallow box disposed immediately beneath the undersurface of the carrier band. 'I'he side walls of the box comprise a pair of parallel strips 36, 88 Awhich are vertically disposed and extend in a direction parallel to the longitudinal axis of the belt. 'I'hese strips are located immediately adjacent two ends of the collector roll (see Figs. 2 and 3) to substantially prevent from pouring over the ends of the roll and into the vat, slurry which has been raised up above the normal level of slurry in the vat by rotation of the collector roll. An end wall of the vbox is defined by a vane or baille I0. Said vane is secured along its upper edge to a shaft l2 extending through somewhat elongated openings in the strips 36, 88 and journaled in the side walls of the vat. One end of the shaft carries an arm 44 (Fig. 4) whose position is controlled by two set screws 48, 48. The

.upper edge of the vane 4U is disposed quite close to the undersurface of the carrier band and is above the normal level of slurry in the vat. The lower edge of the vane, whose position can be adjusted by manipulating the set screws 48, I8, is disposed near the turning surface 'of the collector roll. This vane acts to dam against movement into the vat slurry which has been raised above the normal level of slurry in the vat by turning of the collector roll. It will be appreciated that the space between the lower edge of the vane and the collector roll will determine the rate at which slurry drains back into the vat and,

- therefore, will regulate the pressure of the raised slurry column against the undersurface of the carrier band.

/ 'I'he strips 38, 38 are supported by flat pieces of spring metal 50 which are carried on angle irons 52 bolted to the side walls of the vat. These springs are so positioned and shaped that the top edges of the strips are pressed slightly against the undersurface of the carrier band and serve to sharply define the front and back edges of the "pressure zone. The leading edge of the pressure zone is roughly marked by the top edge of the vane lil-actually the zone terminates short of said vane. The trailing edge of the pressure zone is approximately marked by the top of the collector roll-actually the zone extends somewhat past this point (see Fig. 5). The slurry, as it is broughtup by rotation of the collector roll, will accumulate in the area bounded by the top of the collector roll, the vanes l and the strips 38, 38. For a distance from the top of the collector roll toward the vane I8 the slurry 4 actually is forced under pressure against the under 'surface of the carrier band. As the level of the raised slurry approaches the vane 4l, it descends slightly to the top of the vane. However, such descent does not extend far back to the collector roll due to the somewhat viscous nature of the slurry and the rapid rate at which slurry is raised into the pressurerone. Thus, over the V zone defined by the aforesaid elements, the slurry will be forced up against the undersurface carrier band under pressure.

It may be mentioned that the collector roll of the and its adjuncts, are particularly well suited to ,uniformly distribute the slurry under approximately uniform pressure 'over an appreciable area of the undersurface of the carrier band so that a uniform layer of slurry will be applied to the band. In addition, the particular apparatus serves to exactly demark the longitudinal edges of the layer deposited on the carrier band. Furthermore, said collector roll will not throw against the undersurface of the carrier band heavy or sharp extraneous objects which may be present in the slurry and which would lessen the already short life of the carrier band. 'I'his latter effect is enhanced by having the outer surface of the collector roll smooth, or even plated.

In order that slurry pressed against the undersurface of the carrier band may be facilitated in its adherence thereto as a layer, and for other reasons which later'will be apparent, there is, in accordance with the present invention, provided above the upper surface of the carrier band. immediately over the pressure. zone, avacuum means such as a suction box 54. Said box is connected by a suitable conduit C" to the intake of avsuction pump 55. The suction box may, as shown, be in the 'shape of hollow, elongated trough whose bottom is closed by a perforate plate 58. Said suction box will suck through the pervious carrier band water in the layer of slurry deposited on the undersurface of said band at the pressure zone. However. the carrier band will prevent any cement or asbestos fibers from passing through so that substantially all of the active materials of the slurry are retained in the layer of cement-asbestos deposited on the undersurface of the band. The water discharged by the suctionpump runs to a storage tank. Said suction box may extend a short distance in the direction of travel of the band (indicated by the arrow A in the various figures) beyond the pressure zone, so as to aid in adhering to the band the layer of slurry applied at the pressure zone and also to assist in making certain that this freshly deposited layer is not too greatly laden down with water.

The slurry in the tank is kept in a constant source of agitation and, therefore, of uniform 'I'he carrier band, after leaving the collector roll I8, enters between the rolls 28, 28, which are idler pressure rolls and are employed to express a substantial amount of water both from the carrier band and the freshly deposited layer of cement-asbestos. The upper of the two rolls may be formed from a resilient material, as for instance rubber. The lower of the rolls is sometimes known as a dandy roll made of foraminous material, e. g., screening, whereby to expedite the squeezing of water out of the cement-asbestos layer. 'I'he water thus expressed is allowed to fall onto the floor, which is sloped toward the storage tank in which water is accumulated and stored in order to recover the cement and asbestos fiber sediment which settles out. The recovered water is subsequently reused.

It is noted in passing that the amount of cement and asbestos fiber which passes to the storage tank is very vsmall in comparison to the amount which reached said tanks in previously 64. In the reach between the two idlers 62,64.

where the cement-asbestos layer is on the upper surface of the carrier band, a pair of suction boxes or other equivalent suction means 68 is disposed against the undersurfacaof the carrier band. 'Ihese boxes pull additional water or watery fluid from the cement-asbestos layer, which fluid gravitated tothe bottom of the layer when the carrier band was reversed or which drained out of the layer after the layer had a short time to set. Said suction boxes also function to suck water or watery fluid out of the carrier band into which such fluid flows when the carrier band is'v reversed.

From the idler roll 64 the band rides on to an accumulator roll 66 to which the cement-asbestos layer from the band is transferred in the form of an elongated, laminated tubular slab 69.

Said accumulator roll is carried by a shaft 'I0 and rests on a motor-driven bottom press roll 12 whereby to aid in transferring the cementasbestos layer from the carrier band to the accumulator roll. The pressure between the accumulator and press rolls is adjustable and may be controlled by journaling the accumulator roll shaft at its opposite ends on pivotally mounted levers L connected to rods R having movable counterweights W shiftable therealong to vary the degree of force with which the accumulator roll bears down against the press roll.

After leaving the press roll the carrier band to the carrier band by a' collector roll of such speed, size and location and with the band traveling at the aforementioned rate is such that five layers of cement-asbestos sumce to make a commercially suitable cement-asbestos board.-

It has been found that the rate at which our machine can manufacture board when operating in the foregoing manner is at least three' times as fast as that of a conventional machine having the same band widthand not employing either the method shown herein or that shown in our copending application. Principally, this higher rate 0f production is due to the fact that the individual layers of the laminated cement-asbestos board are thicker than heretofore.

With a collector roll o f the size, speed and location mentioned and with the carrier band traveling at the rate set forth, the vane 40 will function properly when its lower edge is set approximately 115 inch away from the collector roll.

During .the operation of the machine, slurry is, of course, constantly fed to the inlet trough and withdrawn from the discharge trough and in the pressure zone slurry is maintained about one travels about idler rolls 14, 16, 18, idler squeeze rolls 88, 82, an idler take-up roll 84 whose position is variable to adjust the degree of tension in the carrier band, and a reversing idler roll 86.

vIn the reach between the idler roll 18 and the squeeze rolls 88, 82, the Aband passes a water spray 88 and a motor-driven whipper 98. From the reversing idler roll 86 the band passes back to the guide roll 24.

In the operation of the machine thus far described, the carrier band can be driven at any suitable linear speed. We have found that a suitable speed is one such as is conventionally employed in the cement-asbestos board industry, being selected to obtain a maximum length and one-half inches above the normal level of the slurry in the vat by the pumping operation of the collector roll I 8. s

Inasmuch as the strips 86, 38 define the sides of the pressure zone, there is no need to scrape off the band any cement-asbestos outside of the area where it is desired to have the same deposited.

In conventional cement-asbestos board manufacturing machines, when the laminated'tube 68 is stripped from the accumulator roll, it still is so wet that it cannot be handled manually or i calendered without tearing the same apart and.

therefore, the slabs of cement-asbestos delivered from the accumulator roll heretofore have been passed to a baking oven where the board was dried out, at least partially, so that it could be manipulated safely.

In contrast to this,.a slab' of cement-asbestos board taken off our accumulator roll, because of the treatment given it in the portions of the machine already described, already has had so vrruch water removed from it that said slab can be handled without fear of tearing, its tensile strength being appreciable. This comparative vdryness of the slab results from various factors and is believed to be due mainly to the presence out a substantial amount of water from thel cement-asbestos layer before the carrier band is reversed and brought over the suction boxes of life of the short-lived vcarrier band. vA typical speed is 100 feet per minute. The collector roll is turned at a suitably high speed to pump enough V of said band. A typical speed for the collector rollv which secures eminently satisfactory results is 235 R. P. M. with a collector roll121/2 inches in diameter spaced of an inch from the carrier band. The layer of cement-asbestos' applied When the cement-asbestos layer formed on the carrier band is transferred to the accumulator roll, several convolutions of the layer are wrapped about the roll. These convolutiofrs are allowed to build up until the laminated tube has reached a sufficient thickness.v By way of example, a typical tube consists of ve layers of laminations, i. e., the cement-asbestos layer transferred from the carrier band to the accumulator roll is allowed to be wrapped five times about the roll before it is stripped therefrom.

As soon as the desired number of laminations have been superposed upon the accumulator roll and one another, the tube is stripped from said roll. The actual stripping process can be achieved in a manner well known in the eld. This conperiphery of the accumulator roll.

sists, for example, in providing the accumulator roll with two slots 82, 04 which run across the face of the roll parallel to the shaft 10 and are diametrically opposed. When in the case mentioned, i. e., with five laminations, the roll has completed 41/2 turns from the time the last tube was stripped therefrom, the operator of the machine runs the tip of an instrument, such as a rod, along the slot which is covered by four laminations. Then when the next slot is covered with nve laminations, he runs the same instrument along said next slot. Immediately thereafter he inserts the tip of .the instrument under the surface of the tube at the trailing edge of the groove in the sense of rotation of the accumulator roll indicated by the arrow B. This causes the slab of laminated cement-asbestos board to start to fall off the tube. It falls to the left, as viewed in Fig. l, over an idling guide roll 08, which ismounted to turn about a shaft running parallel to the accumulator roll 10 and is located just below said roll at the lower lefthand quadrant thereof so that the guide roll will receive the leading edge of the slab as it drops oil of the accumulator. roll. The slab is led by the guide roll to an endless conveyor belt 98 driven in such direction that the upper reach thereof moves away from the accumulator roll. At the time of delivery of the slab onto the belt 80, said belt is driven at a speed slightly in excess of the linear speed of travel of th As the accumulator roll continues to turn, the slab will be led onto the belt 98 until the slot which nrst had the instrument slid therethrough reaches the guide roll 98. At this time the instrument is again traversed through said slot to sever this slab from the remainder of the laminated tube still on the accumulator roll. Then the operator inserts the instrument beneath the trailing edge of the last-mentioned slot to strip the leading edge of the next slab from said roll. This slab too thereupon commences to fall over the guide roll 8i and is fed onto the belt 00. As the machine continues to operate, the

. next slot will be reached, which marks the end of the last slab to be stripped. When such slot passes a point just above the guide roll 86, the second slab being delivered to the belt 88 will be ripped from the layer of cement-asbestos being wrapped around the accumulator roll because of the higher speed of travel of the belt 88. This action prevents the stripping from the accumulator roll of the single layer of cementasbestos which is being transferred to said roll from the carrier band and therefore allows the next laminated tube to start building up. It therefore will be appreciated that the over-speed of travel of the belt in comparison to the linear speed of travel of the periphery of the accumulator roll is a feature of the invention.

The length of the upper reach of the belt 88 is in excess. of the peripheral distance around the accumulator roll so that said reach can accommodate the length of the slab or slabs delivered during one revolution from the accumulatorroll. Said belt leads the slabs to a pair of calendering rolls |00, |02. These rolls are pressed together by any suitable means well known to the art, as for example spring means or hydraulic means (not shown). Optionally, the lower roll |02 vis journaled in stationary bearings and the upper roll |00 in movable bearings to which a suitable downward pressure is imparted. Preferably, the lower roll |02 is smooth and, if desired, the upper roll |00 likewise may be smooth,

yin which case the calendering rolls simplyserve Vsome desirable design to one surface of the slab.

One such design consists of a wood grain and another simply of a series of parallel scorings ir. the slab, which, of course, are not made sufficiently deep to detrimentally affect the strength of the slab either when damp or after the slab hasbeen allowed to set.

The calendering rolls are motor-driven, preferably at a speed considerably below that at which the slabs are delivered from the accumulator roll in order to prevent tearing orcracking of the slab. These different rates of speed may be employed since the a-ccumulator roll only delivers slabs once every five revolutions thereof.

To enable the machine to operate in this fashion, the belt 88 which leads slabs from the accumulator roll to the calendering rolls is so driven that it can be operated at two speeds, one speed-the high speed-being slightly in excess of the linear speed of the accumulator roll and the other speed-the low speedbeing matched to linear speed of the calender rolls. To this end. the belt 90 runs over two rollers |08, |08, the latter being driven by suitable means, such as a chain ||0, from a two-speed motor ||2 or any other two-speed suitable source of power. These speeds are so selected with respect to the reduction effected by the chain drive that, at the higher speed of the motor H2, the requisite high speed of the belt 00 will prevail and at the low speed of the motor H2, the proper low speed drive of the belt will be obtained.

The two-speed motor is of any conventional type and may be of the kind in which the selection of speeds is controlled by the use of relays. The motor is regulated by a two-pole, doublethrow snap-action momentary electric switch I I4 of the kind, for example, known as a micro switch in the electrical field. This switch has a sensing means in the form of an actuating finger I I8 which is biased toward the belt 88 and whose tip is adapted to press against the upper reach of the belt 08 above the roller |00 at the delivery end of said belt.

When the switch touches the surface of the belt, i. e., when no slab is presented at this point, the switch lll controls the motor ||2 in a manner well known in the art so that this motor runs at high speed. At such time, therefore, the belt 98 moves rapidly and is ready to receive a slab from the accumulator roll. When the leading edge of the slab moves beneath the tip of the ilnger H8, it will raise said finger to its second position, in which the switch causes the motor |12 to operate at its low speed. Thus, as the slab is delivered to the calendering rolls by the belt 80, the speed of the slabs suddenly will be checked to match the linear speed of the calendering rolls. The speed of the calender rolls is suillcientlyfast to enable both slabs to be calendered before the following pair of slabs is de- 9'- livered to-the belt u from the-calendering roll.-

l l in the direction of rotation of the roll whereby .to dam above the normal level of the slurry in the vat a quantity of slurry raised by rotation of the roll, and means including a suction device? abovethe band to create a vacuum at the upper surface of said carrier band above said roll.

3. An apparatus as set forth in claim 2 wherein the memberlying across the roll can be moved toward and away from the surface of the roll .so as to regulate the damming effect on the 'slurry raised by rotation of the roll.

between the delivery roll |08 of the belt. and

the entry point of the calendering rolls and another supporting platform |24 interposed be` tween the discharge point of the calendering rolls and the pick-up roll |26 of the belt ||8.

l adapted to contain cement-asbestos slurry, means to feed slurry to said vat, means to deliver from f After the slabs have been transferred to the.

table they are stored under cover at ambient temperature until they have dried and set suilicientl'y to be cut to shape. 'Ihis may involve from one to three days. depending upon weather conditions.

It will thus be seen that we have provided an apparatus which achieves the several objects ofmeet tue` our invention and is well adapted to conditions of practical use.

As various possible embodiments might'be-made n of the above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense. I

Having thus described our invention, we claim as new and desire to secure by Letters Patent:

1. In an apparatus for manufacturing cementasbestos board, the combination of, a molding vat adapted to contain cement-asbestos slurry, means to feed slurry to said vat, means to deliver from said vat slurry above a pre-determined normal level a pervious fibrous carrier band, means to move said carrier band past and over said vat, an imperforate roll mounted to rotate about a horizontal axis in said vat with the upper'portion thereof above the normal level of slurry in the vat and below the undersurface of the carrier band, means to rotate'said roll,.a member ex- Y tending transversely of the roll and damming at alevel above the normal level of the slurry in the vat over a pre-determined zone spaced from the sides of the vat a. localized quantity of slurry raised from the slurryvin the vat by rotation of the roll, and pressed thereby against the undersurface of the carrier band over said pre-determined zone and means including a suction device above the band to create a vacuum at the upper surface of said carrier band above said roll.

2. In an apparatus for manufacturing cementasbestos board, the combination of, a molding vat adapted to contain cement-asbestos slurry, means to feed slurry to said vat, means to deliver from said vat slurry above a pre-determined normal level a pervious fibrous carrier band, means to move said carrier band past and over said vat, an imperforate roll mounted to rotate about a horizontal axis in said vat with the upper portion thereof above the normal level of slurry in the vat and below the undersurface of the carrier band, means to rotate said roll, members dis posed alongside the ends of the roll, a member lying across the roll and extending above the normal level of slurry in the vat, said last-named member being spaced from the top vof the roll 4. In an apparatus for manufacturing cement# asbestos board, the combination of, a molding vat said vat slurry above a pre-determined normal level a pervious fibrous carrier band,means to move said carrier band past and over said vat, an imperforate roll mounted to rotate about a horizontal axis in said vat with the upper portion thereof above the normal level of slurry in the vat and below the undersurface of the carrier band, means to rotate said roll, a pair of members mounted alongside the ends of said roll and extending parallel to the direction of the movement of the band, the upper edges of said meinbers contacting the undersurface of the carrier band, another member extending across said 1011, said member being spaced away from the top of said roll in the direction of rotation of said roll, the upper edge of said member being ad-` jacent the undersurface of the carrier band and thelower edge of said member being adjacent the roll whereby a 'localized quantity of slurry raised from the slurry in the vat by the rotation of the roll is dammed at a level above the normal level of the slurry in the vat and is pressed against the undersurface of the carrier band over a predetermined zone spaced from the sides of the vat. and means including a suction device above the band to create a vacuum at the upper surface of said carrier band above said roll.

5. An apparatus as set forth in claim 4 wherein means is provided to resiliently urge the pair of lrneirdibers against the undersurface of the carrier 6. An apparatus as set forth in claim 4 wherein means is provided to adjust the spacing between the lower edge of the last-named member and the roll.

7. In an apparatus for manufacturing cementasbestos board, the combination of, a molding vat adapted to contain cement-asbestos slurry, means to maintain cement-asbestos slurry in said vat at a predetermined normal level, a pervious fibrous carrier band, means to move said carrier band past and over said vat, an imperforate roll mounted to rotate about a horizontal WILLIAM BERNARD. JOSEPH BERNARD.

(References on following page) v REFERENCES CITED Number The following references are of record 1n the 2'052'745 111e -o this patent: UNITED STATES PATENTS 213552606 Number Name Data 2.411.416

440,750 Shinn Nov. 18, 1890 1,708,724 Haug Apr. 9, 1929 1,859,986 Saunders May 24, 1932 Number 1,879,797 Ellis Sept. 27, 1932 10 677.683 2,046,271 Lane et al June 80. 1986 Name Date Binz Sept. 1', 1936 Wright Aug. 29, 1939 Leonard Dee. 26. 1939 Millspauzh, Aug. 1, 1944 Dieckbrader Nov. 19, 1946 FOREIGN PATENTS County Date Germany Dec. 1, 1939 Germany Dec. 16. 1929 

4. IN AN APPARATUS FOR MAUFACTURING CEMENTASBESTOS BOARD, THE COMBINATION OF, A MOLDING VAT ADAPTED TO CONTAIN CEMENT-ASBESTOS SLURRY, MEANS TO FEED SLURRY TO SAID VAT, MEANS TO DELIVER FROM SAID VAT SLURRY ABOVE A PRE-DETERMINED NORMAL LEVEL A PERVIOUS FIBROUS CARRIER BAND, MEANS TO MOVE SAID CARRIER BAND PAST AND OVER SAID VAT, AN IMPERFORATE ROLL MOUNTED TO ROTATE ABOUT A HORIZONTAL AXIS IN SAID VAT WITH THE UPPER PORTION THEREOF ABOVE THE NORMAL LEVEL OF SLURRY IN THE VAT AND BELOW THE UNDERSURFACE OF THE CARRIER BAND, MEANS TO ROTATE SAID ROLL, A PAIR OF MEMBERS MOUNTED ALONGSIDE THE ENDS OF SAID ROLL AND EXTENDING PARALLEL TO THE DIRECTION OF THE MOVEMENT OF THE BAND, THE UPPER EDGES OF SAID MEMBERS CONTACTING THE UNDERSURFACE OF THE CARRIER BAND, ANOTHER MEMBER EXTENDING ACROSS SAID ROLL, SAID MEMBER BEING SPACED AWAY FROM THE TOP OF SAID ROLL IN THE DIRECTION OF ROTATION OF SAID ROLL, THE UPPER EDGE OF SAID MEMBER BEING ADJACENT THE UNDERSURFACE OF THE CARRIER BAND AND THE LOWER EDGE OF SAID MEMBER BEING ADJACENT THE ROLL WHEREBY A LOCALIZED QUANTITY OF SLURRY RAISED FROM THE SLURRY IN THE VAT BY THE ROTATION OF THE ROLL IS DAMNED AT A LEVEL ABOVE THE NORMAL LEVEL OF THE SLURRY IN THE VAT AND IS PRESSED AGAINST THE UNDERSURFACE OF THE CARRIER BAND OVER A PREDETERMINED ZONE SPACE FROM THE SIDES OF THE VAT, AND MEANS INCLUDING A SUCTION DEVICE ABOVE THE BAND TO CREATE A VACUUM AT THE UPPE SURFACE OF SAID CARRIER BAND ABOVE SAID ROLL. 